<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title></title>
	<script type="text/javascript" src="common.js"></script>
	<style type="text/css">
		#box{
			position: absolute;
			width: 800px;
			height: 600px;
			border: 1px solid yellow;
			background: rgb(0,0,0);
		}
		#dv{
			position: absolute;
			width: 15px;
			height: 20px;
		}
	</style>
</head>
<body>
<div id="box">
	<div id="dv"></div>
</div>
</body>
<script type="text/javascript">
	my$("dv").innerHTML = "<span>★<span>";
	my$("dv").firstElementChild.style = "color:yellow";

	window.setInterval(function(){
		var x = parseInt(Math.random()*800);
		var y = parseInt(Math.random()*600);

		my$("dv").style.top = y+"px";
		my$("dv").style.left = x+"px";
	},10)

</script>
</html>